Filter assemblies are used in many industrial facilities to selectively remove material from liquid-state process streams. Filter assemblies are used to both remove undesirable contaminates from process streams and to remove desirable filtrates out of process streams. One type of filter that is employed in many industrial processes includes a bag-type filter element. As the name implies, the actual filter media of these filters is a flexible material such as woven polypropylene. The filter media is shaped to form an elongated bag having an open end and a closed end. The filter element is disposed in an elongated housing so that the open end is located adjacent the top of the housing. The process stream to be filtered is introduced into the top of housing so that it flows through the open end of the filter bag. The material is then trapped by the media and the filtered process stream flows out through the sides and closed bottom of the filter bag. The filtered process stream is discharged through an opening in the bottom of the filter housing.
U.S. Pat. Nos. 3,771,664 and 4,157,964, owned by the assignee of this application and incorporated herein by reference, disclose two known bag-type filter assemblies. More specifically, these patents disclose mechanisms for securing the top open end of the bag-type filter element into the top of the complementary housing. A satisfactory mechanism for securing a filter element in a housing must accomplish two tasks. First, it must secure the filter bag in the housing so that the top of the bag, referred to as the rim, is held in place. Secondly, the mechanism must provide a seal between the rim of the filter element and the surrounding, complementary component of the housing to which the rim is mated. This seal is important because, if it does not exist, the process stream, which is under pressure, can flow in the interstitial space around the rim. If this flow occurs, than at least a fraction of the process stream bypasses the filter and flows out of the filter assembly in the unfiltered state. It should thus be clear that for any bag-type filter element to function properly, a very strong seal needs to be formed around the open end of the bag.
The above patents disclose securement mechanisms, called seal compressors, that maintain good, liquid-tight seals around the open end of a bag-type filter element. A typical seal compressor includes a compressible seal that is located around the open end of the bag. Disks are employed to compress the seal against the housing in order to form a liquid-tight barrier.
While seal compressors work well for establishing a seal around the open end of a bag-type filter element, there is a disadvantage associated with their use. Specifically, a seal compressor is formed out of a large number of components. Providing and assembling these components together can significantly add to the overall cost of providing a filter assembly with a bag-type filter element. Also, a seal compressor must be partially disassembled and then reassembled whenever a filter assembly is serviced. Clearly, the time it takes to perform these processes adds to both the overall time it takes the technician to service the filter assembly and the time the assembly is out of service.
Also, it has recently become desirable to provide bag-type filter elements with handles that extend upwardly from the open end of the filter bag. Providing a filter bag with these handles facilitates the removal of the bag especially when it is weighted down with a large volume of removed material and any unfiltered liquid. However, if the handles are not properly aligned, they may be positioned in the path of process stream that is introduced into the filter assembly. If this occurs, the handles could be subjected to the substantial force that is presented by the pressure head of the process stream introduced into the filter assembly. Over time, there is a possibility that this force can weaken the connection between the handle and the component of the filter bag to which it is connected. If this connection is sufficiently weakened, the handle can be torn away from the filter bag while the bag is in use. Alternatively, the handle could separate from the filter bag as it is used to lift the filter bag from the filter assembly. In either case, the usefulness of the handle would be lost.